Teustee



(No Model.) 8 8 sheetsfsheen 2.

F. M. LYTLE 8 J. A. M-QGOY. TELEPHONE CENTRAL OFFICE APPARATUS.

No. 294,482. Patented M881-.4, 1884. I

Genelulal' l N4 PETERS, Phnllimnmplwr. washington uc 3' Sheets-Sheet 3.

(Nd Model.)

I'. M. LYTLE & J. A. MGGOY.

TELEPHONE CENTRAL OFFICE APPARATUS.

'Patented Mar. 4,-188`4.-

INVE NTORS, @Lyne ala.-

N. PETERS, Pnnw-Lnnagnplwr. wushmgum n.6.I

UNITED STATES PATENT OFFICE.

FELTON M. LYTLE AND JOHN A. MCCOY, OF BALTIMORE, MARYLAND, ASSIGN- ORS TO HENRY B.. LYTLE, OF BOSTON, MASSACHUSETTS, TRUSTEE.

TEI- EPI-loral-z` CENTRAL-OFFICE APPARATUS.

.SPECIFICATION forming part' o f Letters Patent No. 294,482, dated March 4, 1884.

Application filed September 25, 1883. (No model.) l

To all whom it may concern.-

Be it known that we, FnL'roN M. LYTLE and JOHN A. McGoY, citizens of theUnited States,

, residing at Baltimore, in the county of Baltimore and/Statev of Maryland, have invented certain new and useful Improvements in Telephone Central-Ofc'e Apparatus, of which the following is a specification, reference being had therein to the accompanying drawings.

Our invention relates to the central-office apparatus for sending and receiving calls to and from subscribers, and for connecting subscribers lines, and also to apparatus whereby a chief operator may have supervision of all thetransi 5 actions of the switch-board operators in their intercourse with subscribers.

Our invention has` especial reference to an improvement in that class of central-office apparatus in which pairs of connecting-cords are 2o used for connecting subscribers lines7 a fair example of such apparatus being shown in the "United States Letters Patent granted to M. G. Kellogg, September 20, 1881, and numbered 247,199, while, however, the improvement lis upon this general class of apparatus, and is de! signed particularly for use in connection with multiple switch boards, as willhercinafter appear. y

It has heretofore been necessary to useasig- 3o naling-key for each connecting-cord, in order that signals may be sent from' the central office to both a calling and a called subscriber,

and in addition to these two keys a separate testing device has been necessary in multiple- 3 5 switch-board systems,in order for the operator to ascertain whether or not a called line'is in use at some other table than his own or grounded for any purpose, the manipulation of this testing device adding to the work and 4o, time required to b e expended by the operator in making connections. It has further been customary to use a listening-key to' connect each pair of cords with the operators telephone when itis desired to ascertain if two' subscribers have finished conversation and' have neglected to send the clearing-out signal.

' The use of such a listening-key is objectionable, from the fact that it grounds both subscribers7 lines at the central-office while they 5o are connected for conversation, and a portion of the .current is diverted from the lines, thus l seriously weakening the operation of the receiving-instruments.

The object of one part of our invention is to simplify thev apparatus by enabling a single pair of signaling-keys to be utilized for signaling with any number of pairs of connecting-cords, thereby greatly reducing the eX- pense of construction and the liability of an operators interrupting connected subscribers by ringing on the wrong line, and, further, to dispense altogether with a separate listeningkey. v

Another part of the invention has for its object to utilize one cord of each pair fortesting at multiple switch-boards, and thus dispense with a separate testing device for each pair of cords.

Another part of the invention is designedV to enable a chief operator, located at any distance, to place his telephone in connection with the connectingcords of any of a number of switch-boards, so as to overhear communications sent over any of the subscribers lines to or from the central office.

With these objects in view our invention consists in certain novel combinations of devices and arrangements of circuits, which will be fully understood from thefollowing particular description, in connection with theaccompanying drawings, in Which- Figure 1 is a perspective view of a multiple switch-board equipped according to our invention, and- Fig. 2 is a diagram illustrating the circuits of the board and the relation of the-variousdevices. Fig. 3 is a diagram illustrating the apparatus of a central office in 4 which there are a number of switch-boards IOO e amaca plate are pcrforations for the passage of the l te., each line being connected through a seconnecting-cords F, each of which has one end connected with metallic plug, as shown atf, the plugs of all the cords resting on the groundplate d.

G and G indicate two signaling-keys for use in connection with subscribers7 lines, and G and an annunciator, e', are used for signaling in connection with the chief operatorls apparatus. Each of the board-sections, it will be seen, is provided with three signaling-keys and the chief operators annunciator.

The letter T indicates the board-operators transmitters, and T their receivers. Upon the shelt1 in front of each numbered board-section is a multiple looping-in switch of the kind shown and described in the patent of H. XV. Breckenridge, granted January 17, 1882, and numbered 252,421.

We will now refer to the diagram Fig. 2, in order to explain the connection of the various devices upon the switch-board, and first we will explain the construction of the multiple looping-in switch or series of looping-in switches upon the shelf. 'A series of metallic standards, 11, is secured to the shelf, and to each of these standards is pivoted a jack, Q, provided with two curved arms projecting in opposite directions, so that they may be swung into contact alternately with metallic springarms R and t', which are secured to the shelf on opposite sides of each jack. Each ot' the spring-arms R is provided with a curved eX- tension, l', which hooks over a metallic rod, S, which is supported by suitable standards in such position that when the spring-arms R are lci't free theinner surfaces of the hooked extensions r will bear against said rod; but when said arms are bent outward by the jacks being turned against them, no portions oi said arms will bein Contact with the rod. The connecting-cords F are. arranged in pairs, there being live pairs shown in the diagram for each numbered section ot the switch-board, though it will be understood that any number of pairs may be used that experience may show to be desirable. One cord of each pair is lettered fz and theothcrf, The cord f of each pair is connected to a jack, Q, of the multiple looping-in switch through a clearingout annunciator, as shown at c c`' c, &c., and the other cord, j, of each pair is connected with the hooked spring-arm opposite thejack to which the other cord of its pairis connected. The spring-arms R are all electrically connected together and to the key G, while the rod S is connected to the key G. The upper contact g of the key G is connected with receiver T through the transmitter, and the upper contact g of the key G is connected directly with the receiver. The lower contacts of the keys are connected together and to the ground through the generator X. The bases of the metallic plugs f rest upon a lnetallic groundplate, d, and theiriplug-pius are adapted to enter the switches y in the usual ina-nner. The subscribers7 lines are indicated by Z, Z2 l,

ries ot' connecting-switches from section to scction of the board, and to a calling-annunciator, as is usual in' multiple switch-boards.

In the diagram Fig. 2 the subscribers7 lines l and lf are shown as connected through the lefthand pair of connecting-cords at the boardsection No. l.

The manner of receiving the call, giving the necessary signals, and making the connections is as follows: lt will be understood that the jacks Q are normally turned against the spring-amps R", dellecting these arms so that their hooked extensions l' are forced out of contact with the rod S'. N ow, when the annunciator-drop of line l falls, the operator takes up the plug of the eonnecting-cordj"Z and inserts its pin in the switch connected with the line Z', and at the same time turns the jack Q, connected with said cord, againstits opposite spring arni, R, and out of contact with the spring-arm R, so that the hooked extension of said arm is allowed to make contact with the rod S. A circuit is thus completed from the calling-subscribers line through the cord f2, jack Q, spring R, to key G, and from back (or upper) contact of key G through the transmitter and receiver, back contact of key G, thence by key G to rod S, spring R', cord f, its plug, and the ground, the normal position of keys G and G being against their respective back or upper contacts. This circuit having been established, the operator, by means ot' his instruments, in the usual manner, ascertains with what line connection is wanted, and then ICO makes thetest to see if the called line is in use i at any other board by touching the metallic frame y of the con nectingfswitch of line Z5 withV Acalled line l5 in the `present instance should be connected for use at anothertablc, there will be a clicking sound in the opcrators receiver, as one side of said receiver will be connected to ground through the test-wire 1, and the cord which is plugged to line Z5 at the other table or other connection from the switch-frames to ground, the other side of the receiver having been put to ground through the cord f l and the subscribers line l. It will be understood that the test-wire yis connected with the frames y of its series of connecting-switches; but it is insulated from the springs gj, to which the subscribers linein its series is connected, and is only grounded by the insertion of a plug into one of the switches, such plug connecting the frame with the spring y, so that the test wire becomes grounded through the frame, the plug, the spring y2, and the subscribcrs line connected to said spring. If, therefore, the clicking sound is produced at thel operators receiver on testing, as before stated, it is an indication that the called subscribers line is plugged for some purpose to one of the connectingswitches in its series at some other board. If it is found that the called line is notin use,

IIO

this being indicated'by theabsence of a clickl same manner that they have been used in coning sound at the receiver on testing, vthe operv-ator insertsthe plug in the switch, having it already in his hand and ready for insertion, and then sends a call over the called line'by pressing down the key G upon its lower contact, which act, it will be seen, completes a circuit from the called line through the cord f3 and its plug to spring-armR, with which said cord is connected; the rod S, with which the hookrof said spring-arm is in contact; .the

key G and the wire'connecting it to the rod; the

lower contact ofthe key, and thence through the generator X to the ground, the operatorstelephone instruments being at the-same time cut out as the key leaves its upper contact. After giving the call the operator releases the key, which again rises to its upper contact, thus bringing the operators instruments into connection with both of the subscribers lines; but they can be immediately disconnected from these lines, as also can the keys G and G', by simply returning the j ack Q to .it-s normal position, after which it will be seen that the circuit is fronrl the calling subscriber--sayline Z- through the cord f2 to the jack Q, and thence `through the spring R and over the cord]v3 to the called subscriber-say line l5.-thetwo subscribers7 lines being thus connected for conversation. The connection having been completed, the two keys are free to-be used in a similar manner with any other pair of the connecting-cords, as all the pairs of cords are connected with the multiple switch in a similar manner, and thus two keys only are needed for'all the pairs of cords, whereas-two signaling-keys are required for each pair of cords at the switch-boards of this class, as heretofore constructed. A

By the old plan of testing it was necessary to take up a separate testing device, make the test and replace it, and'then pick up the connecting-cord and insert its plug at the switch if the called line was found free, while by our improvement we economize in construction by Vdispensing with the separate testing device, and we save time and work for the operator, .as when the called line is found free the plug is alreadyat the point where it is to be inserted, and the operator is not required to replace one device and take up another.

It will beobserved in the diagram Fig.v

2 that a single battery-cell, is included in the loop with the receiver at each section of the board, and it is the current of this battery which produces the clicking sound in the receiver when on testing a subscribers line which is called it is found in use orconnected for any purpose which would render another connection with it improper.A

It will now be observed that after t-he lines are connected and the jack returned to its normal position, the operators keys G and G and his transmitter and receiver are free to be used in connection with any other pair of cords in receiving calls and making connections between vany other two subscribers7 lines ,in the nection with the pair of cords connecting lines Z' and l, and thus the two signaling-keys are utilized for performing the same service whi ch 'has required a large number of keys heretoforethat is, at least two keys with every pair of cords.

It 'will also be observed that when any two lines are connected the operator can place his receiver in listening connection therewith by turningthe jack Q, through which the cords are connected, so that it will contact with its i opposite spring, R. The circuit in such case having been already described, it is unnecessary to trace it again; but we would call attention to the fact that no ground-connection` is madevin thus establishing the listening-connection; but the receiver is simply looped into circuit,so that none ofthe current is withdrawn from the connected lines, and the operation ofv their receivers is therefore not weakened or interfered with in any manner.

Referring now to the diagram Fig. 3, we will explain the manner of connecting a number of switch-board apparatuses with the apparatus of the chief operator according to our invention. The several switch-boards 'are designated by numbers, and lthe letter V designates the chief operators table, upon which islocated a multiple looping-in switch similar to vthat at each numbered section of the switchspri Iig-arms R are connected through his transmitter Tito one binding-post of his receivingtelephone T3, the other binding-post of which is cQnnected to the rod S of his multiple looping-in switch. It will `now be seen that the chief operator, by turning his jack in any loop, i

.may bring his telephone-instruments in circuitv with those of any operator at the switch-board,

and he may thus overhear the operators7 com-v v munications with subscribers.

p On each operators table is a key, G2, having its upper contact connected with the ground through an annunciator, z, and its lower contact to ground through agenerator, X. All the operators keys 'Gl are connected to similar keys, G3, on the chief operators table, having their upper contacts connected to the ground respectively through annunciators z and their lower contacts connected to the ground through a generator,X2. It will be seen then that each operator, by these keys and annunciators, may call I r the chief," and the chief may at any time call either of the operators.

In order that the chief operators instruments and-those .of any operator may be put in connection for holding conversation, the chief simply turns his jack connected with the operators7 instruments against its contactspring R, and a communicating circuit is thus completed from one side of the chief s transmitter over the wire w, spring R, jack Q', wire wi, operators receiver, thence through his transmitter and key G, andthence through the spring-arms It and either of his jacks, which he should turn in contact with one of said springs, from this jack over its cord f2, and through the ground-plate to the other cord of the pair, thence over the hooked spring-arm with which said cord is connected, and over the rod S, wire 1v, and to wire to, which is part of loop to chief operator-s multiple switch, rod S of said switch, wire w", through the chief operators receiver, and to the opposite sides of his transmitter from whence the cir'cuit started.

Then conversation has been finished between the chief and one of the switch-board operators, the parts are to be restored to their normal positions in the manner already described.

In the diagram Fig. 3 the chief operators instruments are shown as connected for communication with the instruments of the operator at switchboard No. l.

Having now fully described our invention, we wish it to be understood that we do not confine ourselves tothe precise devices and arrangement of circuits as shown in our drawings, but may vary the same in any manner for the better or more convenient carrying out of the essential principles of our invention.

The combination of the cords and metallic plugs with a metallic ground-plate is intended to form the subject of a separate application for patent.

Vhat we claim is- 1. The combination, with a series of pairs of connecting-cords arranged to connect subscribers7 lines and two signaling-keys, each having a contact-point connected with a generator, of a series of switches arranged to,conneet either of the pairs of connecting-cords with said two signaling-keys, respectively, substantially as described.

2. The-combination,with the series of pairs of connecting-cords arranged to connect subscribers7 lines, and two signaling-keys having contact-points, with which they are normally in contact, connected to the opposite terminals, respectively, of a circuit including a telephone, and opposite contact-points, each connected with agenerator, of a multiple loopingin switch and connections, arranged to place the cords of any pair separately in 'connection with said two keys, respectively, substantially as described.

3. The combination, with thc series of pairs of connecting-cords, of the multiple loopingin switch, having a separate jack or movable metallic part connected with one cord of each pair, a resilient contact-point in connection with the other cord Yof each pair, a common conductor arranged to make contact with said 6 5 resilient contactpoints when the latter arey not in contact with the jacks, and to break contact therewith when in contact with said jacks, the opposite contact-points electrically connected together, the two keys connected 7o to said opposite contact-points and the common conductor, respectively, and the generator,y arranged for connection with both of said si gnaling-keys, substantially as described.

4. The combination, with a pair of connect- 7 5 ing-cords provided with metallic plugs and arranged for connecting.subscribers lines, of an electro-motive instrumente-as, for instance, the operators receiver-and atesting-battery arranged for operative intermediate connec- 8o tion with said cords, and a switch for effecting such connection, whereby, when such connection has been made and one of the cords plugged to a calling-line, the other cord is properly connected for testing another line, substantially as described.

5. The combination of one or more pairs of connecting-cords, a telephone, a testingbattery connected with said telephone, and. a switch and connections arranged to connect 9e said telephone and testing-battery simultane- 4ously in circuit between the two cords of a pair, substantially as described, and for the purpose set forth.

6. The combination,with a series of switchboards or switch-board sections, each provided with subscribers line terminals and pairs of connecting-cords, a multiple loopingin switch, two signaling-keys arranged for connection with the cords, and telephone-instru- Ioo ments, as described, of the chief operators apparatus having a series of switches and a set of telephone-instruments arranged t0 be connected by said switches with the telephoneinstruments of the switch-board operators, respectively, substantially as described.

7. The combination, with a series of switchboard apparatuses, each provided with pairs of connecting-cords and a multiple looping-in switch, two signaling-keys, and telephone-in- 11o struments, connected as described, of the chief operators apparatus, provided with a multiplc looping-in switch, having jacks connected in loops with the switch-board operators telephones, hooked spring-arnis connected also in I 15 said loops, and the opposite spring-arms, and a conducting-rod connected with the opposite terminals of a circuit including chief operators telephone, substantially as described.

In testimony whereof we aiiix our signatures I 2o in presence of two witnesses.

FELTON M. LYTLE. JOHN A. MCCOY.

Vilitnesses:

C. F. McCULLoH, R. K. LEWIS. 

